Structural engineering of imidazolium-based cationic polymers for simultaneous capture of radioactive iodine and pertechnetate in nuclear waste remediation

Radioactive iodine (I 2 , CH 3 I) and pertechnetate (TcO 4 − ), both byproducts of uranium and plutonium fission processes, make up the majority of long half-life radionuclide waste from nuclear power plants. Imidazolium-based cationic polymeric networks (CPN-tib- x ) were rationally designed by modulating benzyl bromide substituents to optimize electrostatic potential distribution and steric hindrance. Representatively, CPN-tib-1 exhibited high efficiency in simultaneous removal of volatile and aqueous I 2 via charge-transfer complexes, affording both adsorption capacities of 5.11 and 1.71 g g −1 , respectively. CPN-tib-3 demonstrated superior CH 3 I uptake (1.54 g g −1 ) through N-methylation at nonionic N sites, surpassing most imidazolium-based materials. More significantly, CPN-tib-2 achieved the highest ReO 4 − (TcO 4 − surrogate) adsorption capacity (921.9 mg g −1 ) as well as fast kinetics through strong anion exchange and electrostatic attraction, maintaining >60 % efficiency even in simulated Hanford low-activity waste (LAW). The impressive ReO 4 − adsorption performance of CPN-tib-2 was attributed to the synergistic effects arising between steric hindrance and densely imidazolium-N + sites. The structure-adsorption performance relationships highlighted the synergy of charge density, steric accessibility, and binding site geometry in governing selective adsorption. This work provides a versatile platform for designing multifunctional polymers tailored for nuclear waste remediation, offering insights into balancing electrostatic and steric effects for efficient radionuclide sequestration.